Shock forming

ABSTRACT

Method of and apparatus for the shock-wave forming of metallic and other workpieces in which an electrical discharge in a liquid produces a shock wave, preferably in a power jet directed against the workpiece. The discharge is produced between a pair of permanent electrodes with a gap between them temporarily bridged at least in part by a fusible conductor. The electrical supply preferably includes at least one high-voltage, low-current source for initiating the discharge and at least one high-current, lowvoltage source for sustaining the discharge thereafter. Control of the power jet is effected by fluidic methods using transverse jets of the same or another fluid, preferably under the control of a programmer.

United States Patent Inoue 1 Feb. 8, 1972 [54] SHOCK FORMING [72]inventor: Kiyoshi lnoue, 100 Sakato, Kawasaki, Kanagawa, Tokyo, Japan[63] Continuation-impart of Ser. No. 735,760, June 10,

1968, Pat. No. 3,566,647.

[30] Foreign Application Priority Data Aug. 17, 1968 Japan ..43/58749Oct. ll, 1968 Japan... ..43/73973 Oct. 11, 1968 Japan... ..43/73974 June10, 1969 Japan... .....44/4553l June 10, 1969 Japan... .....44/45532Jan. 31, 1969 Japan ..44/8455 [52] US. Cl ..72/56, 29/421, 219/76 [51]Int. Cl ..B2ld 26/12 [58] Field ofSearch ..72/56; 29/421; 219/76 [56]References Cited UNITED STATES PATENTS 2,559,227 7/1951 Rieber ..72/563,093,770 6/1963 Wesley et a]. 3,149,372 9/1964 Stinger ..72/56 3,232,085 2/1966 lnoue ..72/ 56 3,232,086 2/l966 lnoue.... ...72/563,267,710 8/ l 966 lnoue.... ..72/56 3,267,780 8/ l 966 Roth ..72/563,234,429 2/1966 Schrom.. ...72/56 3,452,565 7/1969 Cadwell. ...72/ 563,461,268 8/1969 lnoue ..2 1 9/76 OTHER PUBLICATIONS The Case forSpark-Discharge. by R. H. Wesley:

pg. 91 of Product Engineering.Oct. 15. 1962 Primary Examiner-Richard J.Herbst Attorney-Karl F. Ross [57] ABSTRACT Method of and apparatus forthe shock-wave forming of metallic and other workpieces in which anelectrical discharge in a liquid produces a shock wave, preferably in apower jet directed against the workpiece. The discharge is producedbetween a pair of permanent electrodes with a gap between themtemporarily bridged at least in part by a fusible conductor. Theelectrical supply preferably includes at least one highvoltage,low-current source for initiating the discharge and at least onehigh-current, low-voltage source for sustaining the dischargethereafter. Control of the power jet is effected by fluidic methodsusing transverse jets of the same or another fluid, preferably under thecontrol of a programmer.

49 Claims, 41 Drawing Figures PATENIEDFEB 8m? 3.640.110

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ATTORNEY SHOCK FORMING The present application is a continuation-in-partof my application Ser. No. 735,760 filed June 10, I968 (now U.S. Pat.No. 3,566,647) as a continuation-in-part of my application Ser. No.574,056 filed Aug. 22, 1966 (now abandoned but replaced by applicationSer. No. 64,104) as a continuation-inpart of application Ser. No. 311,061 of Sept. 24, 1963, since issued as U.S. Pat. No. 3,276,558 andapplication Ser. No. 508,487 filed Nov. 18, 1965; of my aforementionedapplication Ser. No. 508,487 (now U.S. Pat. no 3,512,384) filed Nov. 18,1965 as continuation-in-part of application Ser. No. 41,080 of July 6,1960, since issued as U.S. Pat. No. 3,232,085; of my aforementionedapplication Ser. No. 574,056 filed Aug. 22, 1966; and of my copendingapplication Ser. No. 696,757 (now U.S. Pat. No. 3,552,653) filed Jan.10, 1968 as a continuation-in-part of application Ser. No. 574,056 ofAug. 22, 1966 and Ser. No. 629,633 filed Apr. 10, 1967 now U.S. Pat. No.3,461,268.

This invention relates to shock-wave forming, using electrical dischargeenergy.

CROSS-REFERENCE TO EARLIER APPLICATIONS In my earlier application Ser.No. 508,487 filed Nov. 18, 1965, I have described an improved electrodeassembly for a discharge-shaping apparatus which imparts relatively longlife to the electrodes and which affords maximum utilization of thedischarge current. Basically, the apparatus described in thatapplication comprises a generally closed container having at least oneflexible wall closely juxtaposed and preferably in contact with theworkpiece and filled with a liquid shockwave-transmitting medium inwhich an electric discharge is effected.

The vessel may have at least one wall defined by an clastomeric membranejuxtaposed with and advantageously in surface contact with the workpiecealong a side of the latter opposite a die whose die cavity is spanned bythe workpiece. The discharge generated by the electrodes in this vesselis flattened or augmented to develop a greater discharge pressure byproviding an interelectrode spacing somewhat larger than is normallysuitable for the generation of a spark discharge and an electricallyconductive body is disposed by the electrodes.

In this case, the discharge apparently is subdivided into a pair ofsomewhat smaller discharges jumping between the intermediate body andthe adjacent electrodes at least during the initial portion of thedischarge when an ionization of the normally dielectric material in theelectrode gaps occurs. Thereafter, the conductivity of the gap increasesrapidly and the discharge appears to bridge the two electrodes directlyin spite of the fact that a conductive member is disposed between them.A single intermediate member can be disposed centrally between the twoelectrodes, according to the system described in application Ser. No.508,487, or else a plurality of equispaced members can be disposed inthe gap as required. The use of such intermediate electrodes has beenfound to sharply increase the discharge pressure available with similarelectrical energy utilization.

In the later application Ser. No. 574,056, I have applied the principlesof high-energy discharge in the propulsion of particulate materials andthe like to coat a substrate, to provide a desired workpiececonfiguration or otherwise modify the workpiece as a result of the shockwave.

Basically, that system resides in a method of coating metallic substrateby juxtaposing a source of a detonation-type impulsive wave with asurface of the body to be coated and disposed between the body and thesource, a mass of a pulverulent materials, preferably in proximity tothe detonation source. The production of the detonation-type wave by thesource drives the particles onto the substrate with a velocitysufficient to enable them to lodge on the substrate with a firm bondbetween the coating layer and the substrate.

In accordance with this process, a layer of powder is supported upon afrangible foil, film, sleeve or sheet juxtaposed with the surface to becoated whereby the resulting rupturable diaphragm can separate thedischarge chamber from the workpiece chamber. The latter is vented tothe atmosphere to prevent the development of pressures resistinghigh-energyrate or kinetic movement of the particles into bondingengagement with the workpiece and the venting means preferably includesa further damping muffler. The frangible diaphragm may constitute acounterelectrode for the discharge system and the arrangement has beenfound to give excellent results when broad surfaces of a workpiece areto be coated. The discharge electrode is a needle spaced from thefrangible foil while the discharge chamber is provided as a dischargegun whose barrel is trained upon the workpiece and receives, at anintermediate location between the mouth of the barrel and thespark-discharge shock-wave generator, a mass or body of particles to bepropelled against the workpiece.

I pointed out further in application Ser. No. 574,056, that thedischarge system may be constituted by a fusible wire which explosivelydisintegrates upon the application of a highenergy electrical pulsetherethrough to form a spark-type discharge in the gap vacated uponfusion of the wire. Alternatively the detonation source may include apair of electrode elements adapted to define between them an electricaldischarge gap, the pulverulent material being disposed in closeproximity to the gap and advantageously surrounding it. The gap may bebridged temporarily by a fusible element which is disintegrated upondischarge of a high-energy pulse across the gap, the fusible elementserving to lengthen the effective time of discharge as a consequence ofthe delayed opening of the gap.

In application Ser. No. 696,757, it is pointed out that heated particlesmay be projected against a workpiece and that the particles can beformed in situ within the barrel of the discharge chamber by thermaldestruction of a fusible material, the thermal destruction beingeffected by electrical disintegration or erosion of the fusible elementby hot gases, preferably in a plasma condition.

A pair of particle-forming electrodes may be provided at a locationahead of the discharge electrodes and may be heated by electricalresistance or arc-forming techniques to vaporize the metal of at leastone of the electrode to produce particles which are totally gaseous orupon condensation or solidification at the temperature within thedischarge chamber, are in a liquid or finely divided solid state.

In effect, the particle cloud is a condensate of a particle sizesubstantially smaller than that of particles of similar materials madeby mechanical comminution techniques.

Still further uses of high-energy spark discharges and explosivedischarges with the aid of fusible electrodes are described inapplication Ser. No. 735,760 which deals with a hydroimpact-formingsystem in which a column of liquid in a barrel of a shock-forming gun istrained upon the workpiece and an explosive-type discharge is effectedin the column to propel the column against the workpiece and generate ashock wave superimposed on the gross movement of the liquid to shape theworkpiece. The liquid is preferably directed at the workpiece in a jetwith a velocity of to 10,000 m./sec. and the discharge is superimposedimpulsively on this jet.

It has been found in accordance with these teachings, that it ispossible to selectively shape large-area metallic bodies or selectivelyto apply high-energy-rate forces to selected regions of a body to bedeformed by training at the workpiece, from a location spaced therefrom,a discharge chamber whose barrel receives a liquid column which ispropelled at least in part by an electric-discharge-induced shock waveagainst the workpiece surface.

When a column of liquid is trained in this fashion upon a limited regionof a workpiece and is constituted as a dynamic force-transmittingmedium, such that it is actually propelled against the surface ratherthan being confined to the function of shock-wave-transmitting medium,highly improved accuracy can be obtained in conforming the workpiece toa die over the accuracy which is possible using systems with arelatively static liquid medium filling a closed space and inforce-transmitting relationship with the workpiece.

The mouth of the barrel and indeed, the liquid level therein is locatedbelow or at a distance from the workpiece surface so that an ambient gasfills the space between the liquid in the barrel and the workpiece. Anumber of such barrels, provided with means for refilling the barrelchambers with a liquid dielectric, are trained at respective regions ofthe workpiece or the discharge gun is constituted as a swingable memberadapted to sweep its impact across the surface. Advantageously, themeans for refilling the barrel may also be used for delivering liquid tothe latter at a rate sufficient to produce a high-velocity jetcontacting the workpiece even in the absence of impulsive or shock-waveforce. This stream may be continuous and/or pulsed to coincide with theelectrical discharge.

BACKGROUND OF THE INVENTION The instant invention is based upon theaforementioned applications and knowledge in the art that it is possibleto shape a workpiece with a liquid-transmitted shock wave produced inpart by an impulsive discharge in or adjacent the liquid medium. Thusthe prior art has recognized, even before the developments set forth inthe copending applications mentioned above, that it is possible to shapea workpiece with the aid of a shock wave produced by spark discharge andwherein the shock-wave-transmitting medium consists of a liquid whichmay be a dielectric in cases in which the discharge energy is to beheightened.

OBJECTS OF INVENTION It is the principal object of the present inventionto provide an improved system for the spark forming of a workpiece inwhich the discharge energy transmitted to the workpiece is increased andcontrol of the discharge facilitated.

A more specific object of this invention is to provide an improvedmethod and apparatus for controlling the hydroimpact high-energy-rateforming of plastically deformable bodies with respect to the directionaleffects of the high-energy-rate forces.

Yet a further object of this invention is the provision of an improvedelectrode system and method of operating same, for use in spark shaping,coating and forming of metallic and other workpieces.

Another object of the instant invention is to extend the principles setforth in the above-mentioned copending applications and generally toimprove the high-energy-rate shaping, coating or forming of plasticallydeformable workpieces.

It is still further an object of this invention to provide a method ofand an apparatus for the efficient, accurate and economical shaping ofplastically deformable bodies of large surface area and complexconfiguration as well as the shaping of workpieces requiring highershaping energy in certain regions than in others.

Still another object of this invention is the provision of a system forthe shaping of metallic and other plastically deformable bodies inselected areas without undue concentration of shaping pressures andforces which may result in tearing and deterioration or undesirablestress of the workpiece.

Still another object of the instant invention is to provide ahydroimpact device with repetitive triggering for the shaping or workingof large-area plastically deformable or frangible workpieces inaccordance with a predetermined program and with optimal forceapplication to selected areas of the workpiece.

SUMMARY OF THE INVENTION These objects, and others which will becomeapparent hereinafter are attained, in accordance with the presentinvention, in a spark-forming or high-energy-rate machining apparatus inwhich an improved electrode system is provided to increase the availableforming energy or power and to control the development of the discharge,whether the device is used to produce a shock wave for statictransmission by a fluid or for the dynamic hydroimpact system describedabove, an improved control arrangement in the barrel of ahydroimpactforming system for controlling the localized application offorming pressure, a system for programming the improved control device,and an improved power supply which has been found to increase shapingaccuracy, especially when used with a fusible conductor gap-firingarrangement as will be described in greater detail below.

When the term spark forming is used herein, therefore, it will beunderstood that to the extent that the invention applies to an improvedelectrode system for generating the shock wave, the expression may referto spark discharge methods and apparatus in which a particulate materialis carried by the shock wave and bonded to a substrate through a gaseousmedium, to a system in which a spark-generated shock wave is transmittedto the workpiece surface by a static liquid medium in contact therewithor to a system in which a circulated liquid substantially completelyfilling the space between the discharge and the workpiece, and tohydroimpact systems in which the shock-wave-transmitting medium is amoving column of liquid. When, however, the invention pertains todirectional control and the programming of hydroimpact arrangements, theterm shock forming may be used exclusively in connection with suchsystems.

According to the principal aspects of the present invention, which makesuse of principles described in the above-mentioned application, shockforming, i.e., the application of one body to another in bondingrelationship, the shaping of a body or the coating of a substrate with aparticulate material, is carried out with a shock-wave-transmittingmedium between a workpiece (e.g., a substrate or a plasticallydeformable metallic or nonmetallic body which may overlie a die cavity)by producing a spark discharge in a fluid medium. The invention makesuse of my discovery that an improved utilization of the electricalenergy and improved control of the discharge may be obtained when thedischarge gap includes a fusible conductor which is explosivelydisintegrated by the application of a high-energy electrical pulsethereacross. A system using a fusible conductor is described and claimedin application Ser. No. 311,061 issued as U.S. Pat. No. 3,267,710, andthe applications which are mentioned above and have extended theprinciples set forth in this application and its parent case. Morespecifically, it has been pointed out in my'pn'or work in this fieldthat an extended discharge with higher useful energy, Le, a greaterefficiency of conversion of the electrical energy into useful work inform of a shock wave, may be obtained with an electrode system in whicha flexible conductor is fed toward a relatively massive electrode and isconsumed by the discharge so that an increasing gap is formed with themassive electrode at which the final discharge is sustained. At theconclusion of this discharge, another length of fusible conductor may befed through an opening in one, or both of the spark-dischargeelectrodes, the spark being initiated by the advance of the fusible wireor the external switching of a high-energy source, e.g., a capacitor,across these electrodes. Such systems have, however, the disadvantagethat the final discharge, after the destruction of the fusibleconductor, causes a deterioration, welding or the like of the mainelectrodes and, especially the electrode through which the fusibleconductor is fed, thereby blocking the channel and obstructing thepassage through which further control feed must occur. Moreover, controlof the breakdown point, when the advance of the conductor is used as aswitching action, high-rate repetition of the discharges and the likeare restricted.

The present invention provides an improved electrode system fordischarge forming, in which a fusible conductor is fed toward adischarge electrode of the spark discharge system; the fusible conductoris provided adjacent the path of the main discharger and in spacedrelationship therewith so that the conductor is not fed through theelectrode but past the latter.

More specifically, a guide-and-feed means is provided for a continuouslength of the fusible conductor or pieces of fusible conductor, in linewith which the relatively massive electrode is provided, the fusibleconductor being fed in a straight or curved path toward the latter.Alongside this path, preferably at an adjustable distance therefrom,there is provided the second electrode in spaced relationship with thefusible conductor so that two discharge gaps may be formed, namely,between the stationary massive electrode and the fusible conductor andbetween the fusible conductor and the other electrode alongside itspath. The fusible conductor may be a rod, wire or band and, inaccordance with a further feature of this invention, the latter may bebent transversely of its direction of feed to stiffen the conductor.

The permanent electrodes are formed, at least at their tips, of amaterial which resists discharge erosion, e.g., of a coppertungsten orsilver-tungsten alloy.

Yet another feature of this aspect of the invention resides in theinitiation of the discharge by the advance of the fusible conductor andthe provision of the fusible conductor as pieces of wire, foil or thelike which are periodically or aperiodically fired into the gap betweenthe permanent electrode members, one of which may be in the path of theprojected piece of fusible conductor while the other is spacedlydisposed alongside this path. Most desirably, the latter electrode is arod, strip or the like extending transversely to the fusible conductoror its path and preferably at right angles thereto, although thelaterally offset electrode may also extend at an acute angle to thepath, preferably in the direction of feed of the fusible conductor.

All three of the critical elements of this electrode system, namely, theelectrode in the path of the fusible conductor, the fusible conductoritself and the laterally offset conductor adjacent the path, may beshiftable toward and away from one of the other elements to control theintervening gap and thereby initiate the discharge when the surroundingmedium is, for example, a liquid dielectric.

According to another aspect of this invention, a hydroimpact,shock-wave-transmitting column of liquid, preferably in the form of ahigh-velocity stream is directionally controlled by providing along thejet at least one transverse control jet which is employed to deflect themain high-energy-rate liquid column. This aspect of the invention isbased upon the discovery that fluidics techniques can be used mosteffectively to accomplish a directional regulation of a high-velocitystream of liquid upon which the shock wave is superimposed so thatbodily swinging, displacing or otherwise modifying the position of thebarrel of the hydroimpact is no longer necessary.

The invention makes use of principles originally set forth inapplication Ser. No. 735,760 for the shaping selectively of large-areabodies and enables control of the high-energy-rate forces applied toselected areas of the body. More specifically, it has been found that byanalogy to the electromagnetic deflection of an electron beam inhigh-energy cathode-ray or other vacuum tubes, a high-velocity liquidstream upon which the shock wave is superimposed can be deflected withrespect to its effective center of force by providing along this tubeand preferably close to the point at which the liquid stream enters thetube, one or more control jets oriented generally transversely to themain stream. The effectiveness of such control jets is most surprisingwhen it is considered that propagation of the shock wave in a liquidmedium is generally omnidirectional. The use of a control jets inaccordance with the present invention, however, allows selectiveimpingement of the forming wave at predetermined areas of the workpiece.The invention is applicable to systems in which a liquid stream isconstituted as a dynamic force-transmitting medium which is actuallypropelled against the workpiece surface rather than merely constitutinga static medium through which the shock wave is transmitted. It ispossible in accordance with the present invention to operate selectivelyon large areas of a body or apply selectively high-energy-rate impactsat selected regions without displacement of the barrel and preferablywith the barrel stationary. A plurality of control nozzles arepreferably provided adjacent the inlet orifice of the barrel which inaccordance with this invention has a cross section smaller than thecross section of the barrel in the region of the control nozzle and atits mouth so that each of the nozzles is trained transversely of theshock-wave stream. The control fluid may be gas or liquid and isdelivered at a pressure which may range from one-tenth to one-fiftiethof the pressure of the shock liquid.

According to a more specific feature of this invention the controlnozzles are operated by a programming device in order to applypredetermined shock-wave pulses to preselected regions of the workpieceand prevent overstressing of the most sensitive areas. My presentinvention also applies an adaptive control system in which the responseof the workpiece to the shock-wave stream is sensed and the direction,intensity and duration of the shock pulses controlled to optimizeforming of the workpiece. The sensing means may respond to the rate ofdisplacement of the workpiece into the die cavity as well as the degreeof such displacement.

A further aspect of this invention resides in the provision of anenergization circuit for fusible-conductor gap-firing arrangements inwhich both a high-energy and low-energy discharge network are connectedacross the spark gap, a lowcapacity high-voltage capacitor being used tofire the gap whereupon a low-voltage high-amperage source sustains thedischarge.

BRIEF DESCRIPTION OF THE DRAWING The above and other objects, featuresand advantages of the present invention will become more readilyapparent from the following description, reference being made to theaccompanying drawing in which:

FIG. 1 is a diagrammatic vertical cross-sectional view of an apparatusfor the hydroimpact forming of a workpiece into a die cavity, inaccordance with the present invention;

FIG. 1A is a horizontal section through the barrel of the system of FIG.1 taken along the line IAIA of FIG. 1 but showing a modified programmingsystem;

FIG. 1B is a diagrammatic cross-sectional view of a sensor system fordetecting the displacement of the workpiece using the system of FIG. 1A;

FIGS. 1C and ID are block diagram representing alternative programmingarrangements for the system of FIG. 1A;

FIG. 1B is a diagram of a system responsive to the parameters of theshock-wave-transmitting liquid and adapted to be used with the system ofFIG. 1A;

FIG. 2 is a vertical section representing a detail of the electrodesystem of FIG. 1;

FIGS. 2A-2D, 2A'2D' and 2A"2D" represent various operating modes of thesystem of FIG. 2, in accordance with the present invention;

FIGS. 3 and 4 are sectional views through a hydroimpact barreldiagrammatically illustrating a modification of the electrode system, inaccordance with the present invention;

FIGS. 5A, 58, 6A and 6B illustrate other modes of operating theelectrode system of FIG. 2;

FIG. 7 is a diagrammatic sectional view of an apparatus in whichindividual lengths of fusible conductors are introduced into thedischarge gap, according to the present invention;

FIG. 7A shows another means for introducing conductors into the gap;

FIG. 8 is an axial cross-sectional view showing another control systemin accordance with the present invention;

FIG. 9 is a detail view illustrating a modification of the controlsystem of FIG. 8;

FIGS. 10 and 11 are diagrams showing a control arrangement for theshaping of large-area bodies, in accordance with this invention;

FIGS. I2, 13 and I4 are circuit diagrams illustrating improved supplyarrangements for the high-energy-rate-forming arrangements of thepresent invention;

FIG. 12A is a graph illustrating the voltage waveforms obtained with thecircuit of FIG. 12;

FIG. 13A is a detail of a modification of the system of FIG. 13; i

FIG. 15 is a diagrammatic elevational view of another electrode systemaccording to this invention;

FIGS. 16A and 16B are opposite end views of the controlguide arrangementof FIG. 15;

FIG. I7 is a view similar to FIG. 15 illustrating another embodiment;and

FIG. 18 is an end view of the conductor used in the system of FIG. 17.

SPECIFIC DESCRIPTION In FIG. I, I show a system for shaping a workpieceIt) to the configuration of a die cavity 11 in a die 12 with which theworkpiece, here a sheet-metal body, is juxtaposed so as to overlie thecavity. A retaining ring I3 may serve to hold the workpiece It in place.

The workpiece is forced to conform to the contours of the die cavity IIby a jet M of liquid which is propelled at high velocity through thebarrel I and upon which is superimposed a shock wave by a dischargegenerator generally represented at 16 in FIG. I. The shock-wavegenerator comprises a housing 17 in line with the barrel l5 and having aforwardly converging wall 17a open at an orifice I712 coaxial with thebarrel 5 but of a cross section which is substantially less than that ofthe barrel. The latter has an open mouth a wider than the orifice 17band trained upon the workpiece 10.

Liquid, preferably water or a dielectric such as kerosene or transformeroil, is supplied at high velocity to the chamber 170 of the shock-wavegenerator I6 by a pump 18 drawing upon reservoir I9 and controlled asrepresented by the unit 20. A pressure-relief valve serves to bypassexcess liquid to the reservoir I8. While the control 20 is shown to beconnected to the pump 19 so as to regulate the rate of fluid flow intothe chamber ll7c, it will be understood that it may be additionally oralternatively connected to the valve 21 to regulate the pressure of theliquid within the chamber 17c and, therefore, the head with which itemerges from the orifice 17b.

While the spark discharge assembly of the system of FIG. 1 is shown onlydiagrammatically, and in structural detail may be constituted as shownin FIG. 2 and may operate in the modes described in connection withFIGS. 2A-2D, 2A'-2D, 2A"2D". FIGS. 5A, 58, 6A and 615, it may also havethe configuration set forth in connection with FIG. 7 or FIG. 7A so asto be fired by introduction of the piece of fusible conductor into thegap and the energization circuit described in connection with FIGS. 12,13 or I4.

The shock-wave generator of FIG. ll includes a source 22 of a relativelythin fusible conductor 23 in the form of a rod, wire, band or strip,which is fed toward an electrode 24 in its path by a motor 25 or otherfeed means under the control of a start-stop regulator 26. The advanceof the further electrode 27, which extends transversely to the fusiblewire 23 and is spaced therefrom by a gap G, is regulated by a motor 28whose pinion 28a meshes with the rack 27a forming part of the electrode27. Another motor control is provided at 29 for the motor 28.

A discharge may be provided across the gap between the mutuallyinsulated permanent electrodes 24 and 27 by a capacitor 39 which can becharged by DC source 3I through the usual charging resistor 32 in serieswith a reverse-surgesuppressing choke 33 upon the closure of a switch 34by a programmer 35 which, in turn, operates the control units 20, 26 and29.

To provide directional control of the liquid jet (forming or power jet)14 propelled at high velocity against the workpiece 10, the barrel I5 isprovided with a fluidics system under the control of the programmer 35and represented diagrammatically in FIG. I. A number of angularlyequispaced nozzle arrays may be provided at 36a, 36b and 360 at variousangles of intersection with the axis of the barrel I5 and the maindirection of the liquid stream 14, but all generally transverse to thelatter and fed by respective control valves 37 which are operated by theprogrammer 35 via a valve control unit 38. The valve 37 is supplied withcontrol jet fluid, e.g., gas or liquid with a pressure between 0.1? and0.05? (where P is the pressure of stream 14 upon emergence from chamber17c) by a pump 39. The latter draws fluid from the reservoir 19, excessfluid being returned by the pressure-relief valve 39a.

FIG. IA shows a suitable programming arrangement for one of the sets ofcontrol nozzles, the control jets of which sweep the main forming streamacross the workpiece in a programmed manner, the system of FIG. 1A beingof course employed in conjunction with that of FIG. I, when for exampleadaptive control is desired. The barrel I5 of FIG. 1A is shown to beprovided (in a plane perpendicular to the axis of this barrel andparallel to the plane of the paper) with an array of nozzles 36aincluding the sets of diametrically opposite nozzles 156a,, 3611,, 361136a 36m, 36 36a. 36a.,. Each of these sets of diametrically oppositenozzles may receive jets moving in opposing directions or in the samedirection as shown in FIG. IB, a drain being provided at 15b (FIG. I)when opposing jets only are used and the deflection of the main stream14 is to be controlled only by the relative intensities of the controljets or their presence or absence.

Each pair of nozzles of each array in the system of FIG. 1B is shown tobe provided with a valve 37 of the type described in connection withFIG. 1 and located between the pump 39 and the barrel 15. In thisarrangement as well, the pressure-relief valve 39a is connected acrossthe pump 39 which draws fluid from the reservoir 19 and returns fluid tothe latter via line 3%.

Each valve 37 is energized by comparator circuits 38a of the programmerwhich may be solely controlled by a memory or stored inputs representedby the taped storage assembly 38b. Preferably however, a clock pulse isprovided at 38c to the comparator 380 which compares the input from thesynchronized tape 3811 with inputs representing the degree of deflectionof the workpiece 10 into the die cavity 11 and the force applied to theworkpiece, e.g., by a matrix of feelers 38:1 in the mold cavity 11. Asshown in FIG. 1B the feelers 381.1, which have no eifect on the shape ofthe mold and are merely pushed inwardly by the deflection force appliedat F and F' to the workpiece, constitute armatures shiftable inrespective electromagnetic coils 38e and generate an output indicatingthe rate of displacement of the respective feelers and thus the rate ofdeflection of the workpiece at each location, as well as the position ofthe feeler, representing the degree to which the workpiece has beendeflected. This feeler matrix constitutes an input to the programmer 38awhich in turn controls the valve 37 to produce the desired workpiececonfiguration with the preprogrammed rates of deflections of the variousportions as represented by the storage or memory 38b.

An alternative arrangement is shown in FIG. 1C wherein the comparator380 receives inputs from the magnetic memory 38b and from the matrix 38dscanned by the clock pulses from a source 38c to produce outputscontrolling the pressure and velocity of the liquid stream 14 asrepresented at 20, the discharge energy of the shock wave as controlledby the programmer 35 by the degree to which line 40 permits capacitor 30to charge, and the jet direction via the control nozzles 36a, 36b and360 as represented by the unit 37 in FIG. 1C.

In the modification of FIG. 1D, the entire workpiece-forming process ispreprogrammed at 35a and is triggered by the clock pulses from source35!) to operate the controls 20, 40 and 37 mentioned earlier. Forfurther adaptive control of the process, an additional feedback may beprovided as represented in FIG. IE wherein a pitot-tube arrangement isshown at 15c in the barrel 15 to feed back a signal representing thevelocity of the jet 14 to the programmer board.

In operation, the advance of the wire length 23 (FIG. 1) to reduce thegap G between it and the electrode 23 in its path and/or the advance ofthe electrode 27 to reduce the gap G between this electrode and thefusible conductor 23 results in a breakdown of both of the gaps G and Gto enable the capacitor 30 to discharge massively through the conductivepath formed by the electrode 24 the gap G, the length of fusibleconductor 23 between the electrodes 24 and 27 and the gap G to consumethe fusible conductor.

Thereafter the discharge bridges the electrodes 24 and 27 as will bedescribed in greater detail hereinafter. The discharge is of anexplosive nature and generates a shock wave which is superimposed uponthe forcible ejection of the liquid stream represented at 14 so that theliquid impinges upon the workpiece 10 and forces it into the die cavity11 and the impulsive discharge is predominantly directed toward theorifice 17b by the walls of the chamber 17c.

The control chamber defined by the barrel 15 ahead of the orifice 17b isprovided with the nozzles 36a and 36c through which a control fluid, inthis case the same fluid as constitutes the forming stream, is injectedtransversely to this stream to deflect the direction of the shock impactinteracting with the power jet to sweep the latter along and selectivelyform the workpiece under the control of the programmer.

As shown in FIG. 1 a control-nozzle arrangement may comprise threearrays of control nozzles 36a, 36b, and 36c which are directed atdifferent angles to the axis of the power jet and, for example, thefirst array 360 may have its nozzles inclined relatively upwardly whilethe second array is directed perpendicularly to the forming jet and thethird array is inclined in wardly and downwardly, each of the nozzles ofeach array being provided with a respective valve arrangement.

It has been found that the location at which the power jet and the shockwave superimposed thereon is effective, the spread of the shock wave andpower jet and therefore its intensity and even the rate of forming ofthe workpiece may be controlled with great precision for repeatedoperations in a predetermined pattern or program. The programmer 35illustrated in FIG. 1 selects one or more of the control-jet nozzles forinteraction with the individual power jet pulses in ac cordance with thepresent invention.

In FIG. 2 there is shown the spark generator for the apparatus of FIG.I. The generator 16 comprises an electrode 24, here formed as a rodextending through an electrically insulating bushing 17d whose head 176is held in the wall of this bushing by a clamping ring 17f bolted to theouter wall of the housing 17.

The electrode 24 is held in a chuck 24a of a piston-andcylinderarrangement mounted in a housing 17: of the chamber 17 and including afixed double-acting cylinder 24b the fluid ports of which are connectedto a control-valve arrangement 24c regulating the advance or retractionof electrode 24. The piston 24d of this arrangement carries the chuck24a and is shiftable to the left to reduce the gap G or to the right toincrease this gap under the control of the programmer 35 which isconnected to the control unit 24 in the usual manner. The wiper 24sengages rod 24 and has a terminal 24e traversing the feedthroughinsulator 17h of the housing 17j and connected to the power supply whichis provided with the battery 31, the switch 34, the choke 33 and thecharging resistor 32 previously mentioned. In this embodiment however,the capacitor 30 may be connected in series with a switch 30a and theelectrodes so that the gap may be fired by breakdown induced by movementof the electrodes or the fusible wire or by closing switch 30a, in thealternative. Switch 30a may also represent an adjustable breakdown gapdesigned to trigger automatically with the buildup of a sufficientlyhigh potential across the electrode system.

The fusible wire 23 is fed to the gap through an insulating sleeve l7jin the housing 17 aligned with the electrode across a diameter of thechamber 17j while the further electrode 27 is disposed axially below thefusible wire 24 across the gap G. A housing 22a is affixed to thechamber 17 and receives the supply reel 22 from which the continuouslength of fusible wire is led into the insulator 17] between a pair offeed rolls 22b which may be of a profile corresponding to that of thefusible conductor as described in connection with FIGS. 15-18. The feedrolls 22b are driven by the motor 25 under the control of unit 26 asmentioned earlier.

The electrode 27 extends through the upright insulator 17k and is heldin a chuck 27a of the piston 27d of a piston-andcylinder arrangementsimilar to that described in connection with electrode 24. The cylinder27b is anchored in the housing 17m which has a feedthrough insulator 27ecarrying the wiper 27e engaging electrode 27 and forming the otherterminal of the power source.

In a first mode of operation (see FIGS. 2A-2D), control unit 24c isoperated to controllably position the electrode 24 at a fixed distance dfrom the point of intersection p of an imaginary extension of electrode27 and the axis A of the fusible wire 23, the path of which isillustrated in dash lines in FIG. 2A. The conductor 23 is then fed untilit contacts electrode 24 whereupon a circuit is closed with a signalgenerating circuit 41 to trigger the programmer and deenergize motor 25of control 26. The position of the fusible wire 23 is then as shown inFIG. 2B and no gap G1 is employed. In the third stage of the triggeringof the discharge the distance D between the electrode 27 and the fusiblewire 23 is reduced by advance of the electrode 27 (FIG. 2C) until thebreakdown gap distance G is reached whereupon a discharge developsbetween the electrode 2 and the fusible wire 23 drawing current from thecapacitor in effectively a short-circuit condition to yield an explosivedischarge which consumes the length d of the fusible wire and thereafteris transformed into a direct discharge between electrodes 24 and 27 (seeFIG. 2D). Of course, this arrangement requires omission of switch 30a ofits closed condition during the entire operation.

In a second mode of operation, using basically the same system,electrode 27 is advanced to the predetennined gap distance G from thefusible wire 23 (FIG. 2C) while switch 30a remains open to allow thepotential in capacitor 30 to charge above the breakdown level of thisgap. The switch 300 is then closed to create the incipient dischargeacross the gap G, whereupon a full explosive discharge flows as shown inFIG. 2D.

In a third mode of operation, also using the basic system of FIG. 2, thefirst step, as represented by FIG. 2A, fixes the desired length of thefusible conductor at d-g where q is a fixed gap to be maintained betweenthe fusible wire 23 and electrode 24 while d is the spacing along thepath of advance of the fusible conductor between electrode 27 andelectrode 24. In this case, the fusible conductor 23 is advanced untilthe spacing of gap G has the dimension q whereupon a signal istransmitted to the motor 25 to terminate advance of the fusible wire. Tothis end, the detector 41 may be a resistance bridge in which one arm isformed by the conductivity cell constituted by the electrode 24, thefusible wire 23 and the gap G. While the predetermined gap spacing G ismaintained, the electrode 27 is advanced (switch 30a being closed) untildischarge is simultaneously formed across the gaps G and G by breakdownof the fluid (FIG. 2C), whereupon a substantial short-circuit conditiondevelops across the capacitor 30 to yield the explosive dischargeconsuming the fusible conductor and bridging the electrodes 27 and 24(FIG. 2D

An alternative to this mode of operation follows the steps set forthuntil the electrodes and the fusible conductors are in the positionillustrated in FIG. 2C while the switch 30a is open and thereupon closesswitch 30a to produce the breakdown initially across the gaps G and Gand finally across the space between the electrodes 24 and 27 as shownin FIG. 2D.

A further mode of operation is illustrated in FIGS. 2A"-2D In thissystem, the motor 25 is controlled to advance the fusible conductor 23through a fixed length l, whereupon the gap G has a gap width q whichmay be undefined. In this case, the consumed length of electrode will asa practical matter be equal to I. Here too, I is less than d or l'-d-gand upon advance of the fusible conductor 23, the electrode 27 may beadvanced (FIG. 28') to produce the incipient spark discharges shown inFIG. 2C" and thereafter the explosive discharge between the electrodesas represented in FIG. 21)".

In FIG. 5A, there is shown another mode of operation in which theelectrode 27 is brought into a position just adjacent the path of thefusible conductor 23 or into contact therewith as the fusible conductoris advanced across this path. When the fusible conductor then reaches apoint at which breakdown occurs in the gap G, the extended length l ofthe fusible conductor is consumed and the discharge bridges theelectrodes 27 and 2 1. The electrode 24 can be advanced after theconductor 23 has been fixed to fire the discharge across the gap G aswell or both fusible conductor and electrode can be moved relatively toinitiate discharge.

In a further mode of operation illustrated in FIGS. 6A and 6B, thelength of fusible wire 23 is first pushed ahead of the electrode 27 andin contact therewith (FIG. 6A) or with a predetermined spacing therefromover the gap G and the other electrode 24 is advanced toward the fusiblewire 23 until the width q of the gap G is such as to enable the systemto fire, thereby consuming the conductor and producing the dischargeillustrated in FIGS. 2D, 2D and 21)".

As can be seen from FIGS. 3 and 4, the electrodes 24' and 27' can lie ina common plane perpendicular to the axis of the power jet and includingthe fusible wire 23' which is here fed diametrically. In FIG. 4, theelectrode 27 is shown to extend at an acute angle to the fusible wire23" in the direction of feed.

FIG. 7 shows an arrangement in which pieces of fusible conductor, e.g.,as shown at 123 are supplied to the gap between an electrode 124 in thepath of this conductor and an electrode I27 extending transversely tothis path. The pieces may be flat leaves, pencillike sections of rod orthe like and are stacked as shown at 123 in a magazine 122 from whichthey are successively driven into the space between the electrodes I24and 127 by a plunger 125 which may be triggered by a control 126 coupledwith an electromagnetic coil 125a diagrammatically shown to surround aportion of the plunger 125. The pieces 123' are stacked vertically inthe magazine, although it is also possible to insert them laterally asshown for the fusible conductor section 123" and as represented by thearrow 123a". A spring 1251) tends to draw the plunger 125 out of themagazine 122 which may have its successive tiers alignable with aninsulating guide sleeve 117d formed in the chamber 117 or may bepermanently aligned with this guide sleeve so that each of the pieces123 or 123" is aligned with the sleeve in turn.

The electrode 127, which may be vertically shiftable in the insulatingsleeve 117n as shown in FIG. 2 to set the desired gap distance G betweenits free end and the path of the fusible wire 123, is connected to oneterminal of a power supply which consists of a battery 131 adapted tocharge the capacitor 130 through a resistor 132 in series with asurge-suppressing choke 133. A switch 134 may be left closed in order topermit the capacitor 130 to charge immediately after extinction of thedischarge across the electrodes 124 and 127. Electrode 124 may also beshiftable in a guide sleeve 117j to set the position of its free end inthe path of the fusible wire 123.

The chamber 117 may open against the workpiece 110 as shown in FIG. 1via a barrel provided with control jets or, as illustrated in FIG. 7,may be supplied with a dielectric liquid by a pump 118 via aflow-control valve 118 from a reservoir 119 while a pressure-reliefvalve 121 is connected between the output of the pump 118 and thereservoir. Return of fluid to the reservoir is effected via line 1117b.

A switch 130a may be provided in the discharge circuit while theworkpiece 110 is juxtaposed with a die cavity 111 and held in placebetween the die 112 and the body of chamber 117.

The gap of the system shown in FIG. 7 can be fired by propelling thelengths of fusible wire 123 in succession between the electrodes I24 and127 after each preceding discharge has quenched. Alternatively, asequencing arrange ment may be used to first fire the length of fusibleconductor 123 into the gap and thereafter close switch 130a to producethe discharge. The system basically operates in the manner previouslydescribed.

It will be understood that the system of FIG. 7 may be provided with thecircuits shown in FIGS. 12-14 and that fusible conductor 123 may befired into the gap through contoured guide sleeves as shown, forexample, in FIG. 15. Control arrangements of the type illustrated inFIG. 10 may of course also be used and a number of discharge tubes witha singlespark generator may be provided as described in connection withFIG. 11.

In FIG. 7A, there is shown a modification in which the magazine 222 ofthe system of FIG. 7 is a barrel which may be carried by the shaft 222aand stepped by a pawl-and-ratchet mechanism 2221; while the plunger 225,operating as described in connection with FIG. 7, propels thepencilshaped length of fusible wire into the gap between the electrodes.The barrel 222 is then provided with chambers 22212 in angularlyequispaced relationship about the shaft 222a and adapted to receive thelengths of fusible wire and then align themselves with the guide sleeves117d.

The system of FIGS. 7 and 7A may thus be operated in several modes. In afirst mode, the chamber 117 is completely filled with liquid and holdsthe workpiece in an original configuration without deformation orprovides a low-forming-rate force to the workpiece, whereupon thedischarge is triggered by firing the length of fusible conductor intothe gap to plastically deform the workpiece to the extent determined bythe generated shock pressure. The introduction of further lengths offusible conductor into the gap will produce successive discharges asrequired. In a second operating mode, the workpiece is preformed byincreasing the hydraulic pressure within the chamber and final shapingis effected by one or more spark discharges. In a third mode ofoperation, the liquid level is located below the workpiece surface sothat a closed space is provided which may be filled with air or isevacuated, the discharge between the electrodes propelling the liquidmass at high velocity toward the workpiece. Finally, a high dynamic flowof fluid can be provided within the chamber 117 upon which the dischargeis superimposed.

In FIGS. 8 and 9, there is shown a system for the adaptive control ofhydroimpact forming, the expression being used here to refer to shaping,cutting, crushing, cladding (the application of a layer or foil of ametal to a metal substrate), lining, forging or stressing of a workpiecein which a column of liquid is projected in the direction of theworkpiece, here represented diagrammatically at 310. The apparatuscomprises a shock generator 317 provided with a pump 318 adapted toproduce a high-velocity stream of liquid in the direction of theworkpiece, the liquid being drawn from a reservoir 31). The upper end ormouth of chamber 317 narrows into an orifice 317b which is surmounted bya barrel 315 defining a first control chamber C and widening at 315ainto a discharge mouth forming a second control chamber C A dischargeelectrode system, which may have the configuration shown in FIG. 2, isprovided in the lower part of chamber 317 as illustrated generally at316. This generator may include an electrode 324 mounted in insulatedrelationship on the wall of chamber 317 in the path of a fusible wire323 fed from a reel 322 in the direction of the electrode 324.Transversely of the fusible conductor 323, there is provided a furtherelectrode 327 which may be advanced and retracted by a motor 328 via arack-and-pinion arrangement represented diagrammatically at 3284. Apower supply of the type shown in FIG. 2 or FIGS. 12I4 may be connectedto the terminals 330b.

As described in connection with FIG. 1, the first control chamber C, maybe provided with arrays of control-jet nozzles 336a and 336brespectively inclined upwardly and downwardly to the axis of the columnof liquid projected against the workpiece 310. The control jets 3360,336b permit deflection of the power jet or shaping of the latter, e.g.,to render it more divergent or more concentrated as required, and alsocontrol of the velocity and energy of the power jet. In addition, theadaptive control system of FIG. 8 provides an adapter 345 in the chamberC which is axially shiftable as shown in two further positions byphantom lines, via a solenoid or hydraulic servo 345g. The outercontours 345b of this adapter body conform to those of the wall 315a ofchamber C and define the cross section of the power jet. Preferably, thechamber C is cup or bowl shaped while the body 345 has the configurationof a cone.

By moving the body 345 in and out in accordance with a predeterminedprogrammer under the control of sensors as described in connection withFIG. 1A, it is possible to concentrate the force of the power jet inconcentric circles as represented at 3450, 345d and 345a and thisarrangement may be used, for example, when the workpiece is to be shapedin a die having an annular groove. If the annular groove is of uniformwidth and depth, the location of the adapter cone in the chamber C canbe adjusted such that the output jet has an annular width substantiallyequal to that of the annular groove when it impinges upon the workpiecesurface. The control noules 3360, 336b are then able to regulate thevelocity, volume and effective force of the jet to suit the depth of thedie groove and the workpiece material so that deformation occurs withoutdamaging the die or the workpiece. Alternatively, the adapter 345 isshifted in and out to sweep the power jet across the annular path. Bysuitable selection of the configuration of the adapter and the chamber Cpractically all workpiece configurations can be formed with ease andaccuracy.

When the die, e.g., 412 has an intricately shaped cavity 411 as shown inFIG. 9, the workpiece 410 is given a preliminary configuration orpreshape so as to generally conform to the die cavity, e.g., byincreased hydraulic pressure in a system of the type shown in FIG. 7, tothe extent that portions of the workpiece bottom on the ridges of thecontour 411 of the die. By then providing an adapter body or adapterbodies of suitable shape, e.g., as shown at 445, it is possible to splitthe power jet into a plurality of discrete power jets whose velocities,volumes and cross sections may differ but are determined in accordancewith the degree to which the workpiece must be deformed and the natureof the contours. Alternatively, control jets may be used as describedabove to direct the power jet to selected areas and then regulate theparameters of the power jet in accordance with the forming requirementsof the particular workpiece.

FIGS. and 11 show an arrangement in which a plurality of hydroimpactguns or barrels 515a, 5 b is provided in an array covering the entirearea of a die cavity 511 formed in the die 512 overlain by the workpiece510. The barrels 515a, 5151: are trained upon the workpiece and may havea common spark-discharge chamber 517 provided with respective sets ofelectrodes 524 and 527, a common pump 518 and reservoir 519, butindividual reels 522 supplying the fusible wire 523 to the respectiveelectrode gaps. The electrodes are connected to power supplies as setforth in connection with FIGS. 12-14 via the terminals 430b. Each of thebarrels 515a, 515b is provided with three sets of control-jet nozzles536a, 536b and 5360, each having respective control valves 537 operatedby a corresponding control 538 from the master computer control 535. Thebarrel are operated in sequence with dynamic parameter control of theliquid columns as described above in adaptation to the particularconfiguration of the workpiece desired.

The power supply of circuit shown in FIG. 12 may be used for theelectrode systems of FIGS. 1-11 and basically comprises a dualarrangement including a high-voltage breakdown power supply which maydeliver relatively little current and, consequently, low-power, and alow-voltage power supply capable of delivering high current to sustainthe discharge and provide the major portion of the power. Of course, anintermediate supply network may be used to bridge the voltage pulseenvelopes of the high-voltage and low-voltage supply network. Thus thecircuit shown in FIG. 12 is provided with an electrode 627 and anelectrode 624 adapted to be bridged in part by a fusible wire 623 fedthrough a guide 617j by motorand-feed means not further illustrated inthis Figure. As noted above, the advance of one or both of theelectrodes and/or of the fusible wire may be used to trigger thedischarge.

The high-voltage power supply makes use of a high-voltage capacitor 630'connected in series with a high-voltage DC source 631', e.g., of apotential above l,000 volts, which is connected across the capacitorthrough a surge-suppressing choke 633 and a charging resistor 632.

In the discharge circuit of the capacitor 630', there is provided aswitch 630a controlled by a breakdown detector 630b' to cut off thehigh-voltage capacitor as soon as the main power discharge is commenced,thereby permitting the gap to quench and capacitor 630' to recharge.

As can be seen from FIG. 12A, the high-voltage capacitor 630' generatesa discharge voltage pulse P of relatively short duration to break downthe gap and initiate the discharge of a capacitor 630" of theintermediate level power supply. This capacitor 630" is connected incircuit with a charge-voltage source 631 of, say, 500 volts DC and acharging resistor 632". A diode 633" in the discharge circuit ofcapacitor 630" blocks opposite-polarity surges through the source 631".Discharge of capacitor 630 superimposes a pulse P upon the pulse ofcapacitor 630' and brings the gap to the point at which discharge of thelow-voltage high current capacitor 630 discharges through the lockingdiode 633. The low-voltage supply also includes a battery 631 in serieswith the charging resistor 632. The long duration of pulse P illustratedin FIG. 12A represents the total period t of the electric dischargesustained between the electrodes and is of course determined by thecapacity of condenser 630. By using a high-voltage supply to break downthe gap and initiate explosive disintegration of the fusible electrode,it is possible to reduce power consumption and facilitate adjustment ofthe waveform.

A similar current is shown in FIG. 13 wherein, however, the maindischarge current is supplied from a low-current source and is notpulsed in the fashion of the circuit of FIG. 12. In this arrangement,the electrode 724 and 727 which are partly bridged by the fusible wire723 from supply reel 722 are energized by a gap-defining high-voltagepower supply consisting of a high-voltage capacitor 730' of lowcapacitance which is charged through a resistor 732 by the high-voltagesource 731 in series with a switch 734'.

In addition, the electrodes may be supplied by a low-voltagehigh-amperage power supply including a stepdown transformer 731a inseries with a rectifier 73lb. The input of the transformer may includethe line terminals 7310 and a choke 733 in series with the primarywinding of the transformer and with a switch 734 which may be triggeredautomatically upon breakdown of the gap by the potential developedacross capacitor 730 to maintain the low-voltage, high-current dischargeuntil switch 734 is reopened or one of the electrodes 724, 727 iswithdrawn to spread the gap to the point to which discharge can nolonger be sustained.

In place of the low-voltage, high-current system of FIG. 13, theautotransformer arrangement of FIG. 13A may be used. In this case theautotransformer 831a is energized by a low line voltage of, say, 30volts at 831a while the output of, say, 200 volts DC is delivered at theterminals 831d to the electrodes 727 and 724. A rectifier diode 83117 isconnected in series with the output of this network while a resonantcircuit may be provided with the primary turns by a capacitor and aninductance as shown at 833. The network of FIG. 13A may also be usedbetween the secondary winding of the transformer of FIG. 13 and theelectrodes 724 and 727.

A modified circuit is shown for the device of FIG. 14 in which again theelectrode 924 lies in the path of the fusible conductor 923 directed bya supply reel 922 and a movable electrode 927 is provided alongside thepath of the fusible conductor. In this case, the high-voltage DC sourcefor firing the gap comprises a high-voltage battery 931 in series with acurrent-limiting resistor 931a and a switch 030a which is opened oncebreakdown has occurred and the discharge is sustained by the low-voltagepower supply. The low-voltage, high-current source comprises the battery931 in series with a charging resistor 932 and a charging switch 934.The charging circuit is applied in parallel to a bank ofhigh-capacitance condensers 930 which are connected in parallel with oneanother and in series with a rectifier 933 to the gap.

EXAMPLE Using a copper plate as the workpiece, the plate having athickness of 3.2 mm., a width of 200 mm. and a length of 400 mm., it waspossible to shape the plate with repeated discharges with a single powersupply circuit of the tape shown in FIG. 2 when the capacitor had acapacitance of 3,100 1F and a charging potential of 8,000 volts withkerosene as the liquid. Each discharge was the equivalent of about100,000 joules. Using a five-section power supply analogous to that ofFIG. 12 but with five capacitors and five capacitor-charging stages withcapacitances of 5, 10, 300, 1,000 and 2,500 uF and voltages of 1,000,2,000, 10,000, 500 and 50 volts, respectively, each firing involved only15,150 joules and forming was accomplished with the 20 discharges asstated.

It has already been pointed out that the thin consumable conductor orfusible electrode of the present invention may have substantially anyconfiguration ranging from the circular cross section rod to a flattenedstrip. It may be noted, however, that a strip or band configuration ispreferred and that it is possible to improve the rigidity of the fusibleconductor as it extends across the gap by imparting a transversecurvature to the conductor as represented in FIGS. 16B and 18.

In the arrangement shown in FIG. 15, the fusible conductor 1023 is fedthrough a sleeve 1017] in one wall of the housing 1017 from the supplyreel 1022 by a motor 1025 which drives the feed rolls 1022b. To adjustthe gap G between the fusible wire 1023 and the fixed opposing electrode1024 in insulating sleeve l017d, there is provided a further motor 10240which is connected by a rack-and-pinion arrangement 1024b with thesleeve 1017j. The laterally offset electrode 1027 may also be shiftableas described in connection with FIG. 2.

While any suitable circuit may be used to apply the discharge currentacross the electrodes 1024 and 1027, e.g., as set forth in connectionwith FIGS. 12-14, the circuit may simply include a capacitor 1030 whichis charged by the DC source 1031 through the resistor 1032 whiledischarge is accomplished via the switch 1030a whose function haspreviously been described. At the inlet side of the sleeve 1017j, thepassage 1017j' has a rectangular and flat configuration (FIG. 16A) whileat its outlet side the sleeve has a transverse curvature which itimparts to the steel band 1023, the latter being relatively long, e.g.,about 100 mm., and nevertheless of sufficient stiffness as a result ofthe curvature to linearly span the gap. The sleeve 1017 is receivedwithin bearings 1017j" of an electrically insulating bushing 1017j' inthe wall of the housing 1017.

In FIGS. 17 and 18, there is shown a modification of the basic system ofFIG. 15 in which the flat band is fed from a supply reel 1122 by therolls 1122b driven by the motor 1125 between the roller bearings 11l7jof an insulating sleeve 1l17j received in the wall of housing 1117 whilethe desired curvature is imparted to the band by a pair of contouredrollers 1150 and 1151 within the chamber. A ledge 1152 is formedalongside the band 1123 opposite the electrode 1127 to further deflectthe band during incipient discharge.

Iclaim:

1. In a method of forming a workpiece by generating a shock wave whichis propagated against said workpiece by electrical discharge in a liquidmedium, the improvement which comprises the steps of:

temporarily bridging at least part of a gap between spacedapartelectrodes in said liquid medium-with a fusible conductor by feeding alength of the fusible conductor to the gap from a location offset fromthe electrodes;

applying an electrical pulse across said electrodes of an intensity andfor a duration sufficient to disintegrate the length of fusibleconductor in said gap and produce an electrical discharge across saidelectrodes;

displacing said liquid medium independently of said discharge in a powerjet trained against said workpiece; and

controlling a parameter of said power jet by directing selectively andgenerally transversely to the power jet at least one control jet of afluid.

2. The improvement defined in claim 1 wherein said length of fusibleconductor is fed along a predetermined path to said gap in the directionof one of said electrodes while the other of said electrodes is disposedadjacent said path and transversely thereto.

3. The improvement defined in claim 1, further comprising the step ofmaintaining a spacing between said fusible conductor and at least one ofsaid electrodes upon the application of said electrical pulse therebycausing an incipient discharge between the conductor and the electrodespaced therefrom prior to disintegration of said fusible conductor.

4. The improvement defined in claim 1, further comprising the step ofinitiating the application of said electrical pulse to said electrodesby relatively displacing said conductor and at least one of saidelectrodes to reduce the distance between them and thereby effectbreakdown of said fluid medium.

5. The improvement defined in claim 1 wherein said control jet iscomposed of the same fluid as the power jet.

6. The improvement defined in claim 1 wherein the control jet isregulated in accordance with a predetermined program.

7. The improvement defined in claim 1, wherein said electrical pulseincludes initial high-voltage, low-current breakdown component followedby a low-voltage, high-current component sustaining the discharge.

8. The improvement defined in claim 1, wherein said fusible conductor isfed to said gap as a continuous strip, further comprising the step ofstiffening said length of said conductor by imparting a transversecurvature thereto at least across said gap.

9. The improvement defined in claim 1 wherein successive lengths of saidfusible conductor are successively propelled into said gap.

10. In a method of forming a workpiece by training thereagainst a powerjet of a liquid and superimposing upon said power jet a shock waveproduced by electrical discharge in the liquid, the improvement whichcomprises controlling at least one parameter of said power jet bydirecting generally transversely thereto a control jet of a fluid at apressure less than that of said power jet.

11. The improvement defined in claim 10 wherein a plurality of controljets are trained at said power jet and are disposed in spacedrelationship therearound, the method further comprising the step ofselectively operating said control jets in accordance with apredetermined program established in dependence upon the desired formingof a workpiece.

12. In an apparatus for forming a workpiece by deformation orkinetically depositing particles thereon by generating a shock wavewhich is propagated against said workpiece by electrical discharge in afluid medium in force-transmitting relationship with said workpiece, theimprovement which comprises:

a shock-wave generator including a pair of spaced-apart relativelypermanent electrodes; means for feeding a length of fusible conductor toa gap between said electrodes from a location offset therefrom;

means for applying an electrical pulse across said electrodes todisintegrate the length of fusible conductor in said gap and produce anelectrical discharge thereacross, said apparatus being a device for thehydroimpact forming of said workpiece and including a housing having amouth trained at said workpiece but spaced therefrom;

means for passing a liquid at high velocity through said mouth to form apower jet of said liquid impinging upon said workpiece and upon whichsaid shock wave is imposed; and at least one control chamber ahead ofsaid electrodes and formed with at least one nozzle trained transverselyto said power jet for directing thereagainst a fluid control jet toregulate a parameter of said power jet.

13. The improvement defined in claim 12, further comprising guide meansfor directing said fusible conductor along a substantially linear pathtoward one of said electrodes, the other of said electrodes beingdisposed alongside said path and generally transversely thereto.

14. In an apparatus for forming a workpiece by deformation orkinetically depositing particles thereon by generating a shock wavewhich is propagated against said workpiece by electrical discharge in afluid medium in forcetransmitting relationship with said workpiece, theimprovement which comprises:

a shock-wave generator including a pair of spaced-apart relativelypermanent electrodes; means for feeding a length of fusible conductor toa gap between said electrodes from a location offset therefrom;

means for applying an electrical pulse across said electrodes todisintegrate the length of fusible conductor in said gap and produce anelectrical discharge thereacross; guide means for directing said fusibleconductor along a substantially linear path toward one of saidelectrodes, the other of said electrodes being disposed alongside saidpath and generally transversely thereto, the means for feeding saidfusible conductor to said gap including a magazine for successivelydisposing individual length of said conductor in alignment with saidguide means; and

means for propelling said lengths in succession to said guide means.

15. The improvement defined in claim 12 wherein the means for feedingsaid length of fusible conductor to said gap includes a supply of acontinuous fusible conductor and feed means for dispensing the conductorthrough said guide means.

16. The improvement defined in claim 14, further comprising meansindependent of said feeding means for relatively displacing at least oneof said electrodes and said conductor to establish a predeterminedspacing therebetween.

17. The improvement defined in claim 14 wherein said apparatus is adevice for the hydroimpact forming of said workpiece and includes ahousing having a mouth trained at said workpiece but spaced therefrom,said apparatus further comprising means for passing a liquid at highvelocity through said mouth to form a power jet of said liquid impingingupon said workpiece and upon which said shock wave is imposed.

18. The improvement defined in claim 12, wherein a plurality of suchnozzles is provided in spaced-apart relationship around said power jet,further comprising programming means connected to said nozzles forselectively operating same with selected control jet intensities.

19. The improvement defined in claim 18 wherein at least some of saidnozzles are oriented at right angles to said power jet and at least onefurther nozzle is oriented at an angle to the axis of said power jet.

20. The improvement defined in claim 12 wherein said means for applyingsaid electrical pulse across said electrodes includes a high-voltagelow-current source connectable across said electrodes to initiate adischarge through said fusible conductor and at least one low-voltage,high-current source connectable across said electrodes for sustainingsaid discharge upon its formation by said high-voltage, low-currentsource.

21 in an apparatus for the hydrocompact forming of a workpiece bytraining a power jet against said workpiece through a barrel andapplying to said power jet a shock wave by electrical discharge in theliquid, the improvement which comprises means along said barrel forcontrolling the parameters of said power jet and including acontrol-nozzle trained transversely to and against said power jet andmeans for supplying a control fluid to said nozzle.

22. The improvement defined in claim 21, wherein the lastmentioned meansincludes a programmer for regulating said power jet in accordance with apredetermined series of instructions determined by the configuration tobe imparted to said workpiece.

23. The improvement defined in claim 21 wherein a plurality of suchnozzles are spaced around said power jet.

24. The improvement defined in claim 21, further comprising a controlbody ahead of said power jet for defining the cross section thereof.

25. An apparatus for forming a workpiece by defamation thereof orkinetic deposition of material thereon with a shock wave generated by adischarge of a fluid medium and transmitted by said medium to theworkpiece, said apparatus comprising:

a first electrode;

guide means for feeding a length of a fusible conductor toward saidelectrode along a feed path;

means for passing an electrical current pulse through said length ofsaid fusible conductor, thereby destroying said length explosively andgenerating the discharge in said fluid medium; and

a further electrode disposed along said path adjacent said conductor andspaced from said guide means and said first electrode, said means forpassing said electrical current pulse through said length of fusibleconductor being connected across said electrodes to develop a dischargetherebetween upon explosive destruction of said length of fusibleconductor.

26. The apparatus defined in claim 25, further comprising a magazinecontaining a quantity of individual length of said fusible conductor andaligned with said guide means for successively dispensing the individuallength and feeding same along said path.

27. The apparatus defined in claim 25, further comprising supply meanscarrying a continuous fusible conductor and aligned with said guidemeans while being intermittently driva ble for feeding successiveportions of said fusible conductor along said path.

28. The apparatus defined in claim 25 wherein said fusible conductor isin the form of a strip, further comprising means for stiffening thelength of said fusible conductor as it is fed from said guide meanstoward said first electrode by imparting a transverse curvature to saidstrip.

29. The apparatus defined in claim 25, further comprising a housingreceiving said electrodes, said fluid medium and said fusible conductor,said housing being formed with a mouth trained in the direction of saidworkpiece but spaced therefrom for propelling said fluid medium againstsaid workpiece.

30. The apparatus defined in claim 25 wherein said fluid medium is aliquid, further comprising means for displacing said liquidindependently of said discharge in a power jet trained at saidworkpiece.

31. A method of deforming a workpiece or kinetically depositing materialthereon by applying to said workpiece a shock wave generated byelectrical discharge between a pair of electrodes spaced apart in adielectric medium, said method comprising the steps of feeding a lengthof a fusible conductor along a predetermined path toward one of saidelectrodes, the other of said electrodes being displaceable toward andaway from said path; connecting a source of stored electrical energyacross said electrodes; and relatively displacing said fusible conductorand at least one of the electrodes to reduce the gap between them andeffect a dielectric breakdown in said fluid medium to generate adischarge and explosive destruction of said length of fusible conductor.

32. The method defined in claim 31 wherein said one of said electrodesis positioned at a fixed distance from a point of intersection of animaginary extension of said other electrode and said path, and saidconductor is fed toward said first electrode, said other electrode beingdisplaced toward said conductor to reduce the gap and cause dielectricbreakdown of said medium.

1. In a method of forming a workpiece by generating a shock wave whichis propagated against said workpiece by electrical discharge in a liquidmedium, the improvement which comprises the steps of: temporarilybridging at least part of a gap between spaced-apart electrodes in saidliquid medium with a fusible conductor by feeding a length of thefusible conductor to the gap from a location offset from the electrodes;applying an electrical pulse across said electrodes of an intensity andfor a duration sufficient to disintegrate the length of fusibleconductor in said gap and produce an electrical discharge across saidelectrodes; displacing said liquid medium independently of saiddischarge in a power jet trained against said workpiece; and controllinga parameter of said power jet by directing selectively and generallytransversely to the power jet at least one control jet of a fluid. 2.The improvement defined in claim 1 wherein said length of fusibleconductor is fed along a predetermined path to said gap in the directionof one of said electrodes while the other of said electrodes is disposedadjacent said path and transversely thereto.
 3. The improvement definedin claim 1, further comprising the step of maintaining a spacing betweensaid fusible conductor and at least one of said electrodes upon theapplication of said electrical pulse thereby causing an incipientdischarge between the conductor and the electrode spaced therefrom priorto disintegration of said fusible conductor.
 4. The improvement definedin claim 1, further comprising the step of initiating the application ofsaid electrical pulse to said electrodes by relatively displacing saidconductor and at least one of said electrodes to reduce the distancebetween them and thereby effect breakdown of said fluid medium.
 5. Theimprovement defined in claim 1 wherein said control jet is composed ofthe same fluid as the power jet.
 6. The improvement defined in claim 1wherein the control jet is regulated in accordance with a predeterminedprogram.
 7. The improvement defined in claim 1, wherein said electricalpulse includes initial high-voltage, low-current breakdown componentfolLowed by a low-voltage, high-current component sustaining thedischarge.
 8. The improvement defined in claim 1, wherein said fusibleconductor is fed to said gap as a continuous strip, further comprisingthe step of stiffening said length of said conductor by imparting atransverse curvature thereto at least across said gap.
 9. Theimprovement defined in claim 1 wherein successive lengths of saidfusible conductor are successively propelled into said gap.
 10. In amethod of forming a workpiece by training thereagainst a power jet of aliquid and superimposing upon said power jet a shock wave produced byelectrical discharge in the liquid, the improvement which comprisescontrolling at least one parameter of said power jet by directinggenerally transversely thereto a control jet of a fluid at a pressureless than that of said power jet.
 11. The improvement defined in claim10 wherein a plurality of control jets are trained at said power jet andare disposed in spaced relationship therearound, the method furthercomprising the step of selectively operating said control jets inaccordance with a predetermined program established in dependence uponthe desired forming of a workpiece.
 12. In an apparatus for forming aworkpiece by deformation or kinetically depositing particles thereon bygenerating a shock wave which is propagated against said workpiece byelectrical discharge in a fluid medium in force-transmittingrelationship with said workpiece, the improvement which comprises: ashock-wave generator including a pair of spaced-apart relativelypermanent electrodes; means for feeding a length of fusible conductor toa gap between said electrodes from a location offset therefrom; meansfor applying an electrical pulse across said electrodes to disintegratethe length of fusible conductor in said gap and produce an electricaldischarge thereacross, said apparatus being a device for the hydroimpactforming of said workpiece and including a housing having a mouth trainedat said workpiece but spaced therefrom; means for passing a liquid athigh velocity through said mouth to form a power jet of said liquidimpinging upon said workpiece and upon which said shock wave is imposed;and at least one control chamber ahead of said electrodes and formedwith at least one nozzle trained transversely to said power jet fordirecting thereagainst a fluid control jet to regulate a parameter ofsaid power jet.
 13. The improvement defined in claim 12, furthercomprising guide means for directing said fusible conductor along asubstantially linear path toward one of said electrodes, the other ofsaid electrodes being disposed alongside said path and generallytransversely thereto.
 14. In an apparatus for forming a workpiece bydeformation or kinetically depositing particles thereon by generating ashock wave which is propagated against said workpiece by electricaldischarge in a fluid medium in force-transmitting relationship with saidworkpiece, the improvement which comprises: a shock-wave generatorincluding a pair of spaced-apart relatively permanent electrodes; meansfor feeding a length of fusible conductor to a gap between saidelectrodes from a location offset therefrom; means for applying anelectrical pulse across said electrodes to disintegrate the length offusible conductor in said gap and produce an electrical dischargethereacross; guide means for directing said fusible conductor along asubstantially linear path toward one of said electrodes, the other ofsaid electrodes being disposed alongside said path and generallytransversely thereto, the means for feeding said fusible conductor tosaid gap including a magazine for successively disposing individuallength of said conductor in alignment with said guide means; and meansfor propelling said lengths in succession to said guide means.
 15. Theimprovement defined in claim 12 wherein the means for feeding saidlength of fusible conductor to said gap includes a supply of Acontinuous fusible conductor and feed means for dispensing the conductorthrough said guide means.
 16. The improvement defined in claim 14,further comprising means independent of said feeding means forrelatively displacing at least one of said electrodes and said conductorto establish a predetermined spacing therebetween.
 17. The improvementdefined in claim 14 wherein said apparatus is a device for thehydroimpact forming of said workpiece and includes a housing having amouth trained at said workpiece but spaced therefrom, said apparatusfurther comprising means for passing a liquid at high velocity throughsaid mouth to form a power jet of said liquid impinging upon saidworkpiece and upon which said shock wave is imposed.
 18. The improvementdefined in claim 12, wherein a plurality of such nozzles is provided inspaced-apart relationship around said power jet, further comprisingprogramming means connected to said nozzles for selectively operatingsame with selected control jet intensities.
 19. The improvement definedin claim 18 wherein at least some of said nozzles are oriented at rightangles to said power jet and at least one further nozzle is oriented atan angle to the axis of said power jet.
 20. The improvement defined inclaim 12 wherein said means for applying said electrical pulse acrosssaid electrodes includes a high-voltage low-current source connectableacross said electrodes to initiate a discharge through said fusibleconductor and at least one low-voltage, high-current source connectableacross said electrodes for sustaining said discharge upon its formationby said high-voltage, low-current source.
 21. In an apparatus for thehydrocompact forming of a workpiece by training a power jet against saidworkpiece through a barrel and applying to said power jet a shock waveby electrical discharge in the liquid, the improvement which comprisesmeans along said barrel for controlling the parameters of said power jetand including a control-nozzle trained transversely to and against saidpower jet and means for supplying a control fluid to said nozzle. 22.The improvement defined in claim 21, wherein the last-mentioned meansincludes a programmer for regulating said power jet in accordance with apredetermined series of instructions determined by the configuration tobe imparted to said workpiece.
 23. The improvement defined in claim 21wherein a plurality of such nozzles are spaced around said power jet.24. The improvement defined in claim 21, further comprising a controlbody ahead of said power jet for defining the cross section thereof. 25.An apparatus for forming a workpiece by deformation thereof or kineticdeposition of material thereon with a shock wave generated by adischarge in a fluid medium and transmitted by said medium to theworkpiece, said apparatus comprising: a first electrode; guide means forfeeding a length of a fusible conductor toward said electrode along afeed path; means for passing an electrical current pulse through saidlength of said fusible conductor, thereby destroying said lengthexplosively and generating the discharge in said fluid medium; and afurther electrode disposed along said path adjacent said conductor andspaced from said guide means and said first electrode, said means forpassing said electrical current pulse through said length of fusibleconductor being connected across said electrodes to develop a dischargetherebetween upon explosive destruction of said length of fusibleconductor.
 26. The apparatus defined in claim 25, further comprising amagazine containing a quantity of individual length of said fusibleconductor and aligned with said guide means for successively dispensingthe individual length and feeding same along said path.
 27. Theapparatus defined in claim 25, further comprising supply means carryinga continuous fusible conductor and aligned with said guide means whilebeing intermittently drivable for feeding successive portions Of saidfusible conductor along said path.
 28. The apparatus defined in claim 25wherein said fusible conductor is in the form of a strip, furthercomprising means for stiffening the length of said fusible conductor asit is fed from said guide means toward said first electrode by impartinga transverse curvature to said strip.
 29. The apparatus defined in claim25, further comprising a housing receiving said electrodes, said fluidmedium and said fusible conductor, said housing being formed with amouth trained in the direction of said workpiece but spaced therefromfor propelling said fluid medium against said workpiece.
 30. Theapparatus defined in claim 25 wherein said fluid medium is a liquid,further comprising means for displacing said liquid independently ofsaid discharge in a power jet trained at said workpiece.
 31. A method ofdeforming a workpiece or kinetically depositing material thereon byapplying to said workpiece a shock wave generated by electricaldischarge between a pair of electrodes spaced apart in a dielectricmedium, said method comprising the steps of feeding a length of afusible conductor along a predetermined path toward one of saidelectrodes, the other of said electrodes being displaceable toward andaway from said path; connecting a source of stored electrical energyacross said electrodes; and relatively displacing said fusible conductorand at least one of the electrodes to reduce the gap between them andeffect a dielectric breakdown in said fluid medium to generate adischarge and explosive destruction of said length of fusible conductor.32. The method defined in claim 31 wherein said one of said electrodesis positioned at a fixed distance from a point of intersection of animaginary extension of said other electrode and said path, and saidconductor is fed toward said first electrode, said other electrode beingdisplaced toward said conductor to reduce the gap and cause dielectricbreakdown of said medium.
 33. The method defined in claim 32 whereinsaid fusible conductor is fed into contact with said first electrode andthereafter said other electrode is moved toward said conductor toinitiate dielectric breakdown of said fluid medium.
 34. The methoddefined in claim 32 wherein said fusible conductor is first fed alongsaid path until it reaches a position at a predetermined distance fromsaid first electrode and thereafter said other electrode is advancedtransversely to said path toward said conductor to a position at whichdielectric breakdown of said fluid medium occurs in the fluid mediumacross the gaps between said conductor and said electrodes to effectexplosive disintegration of said conductor and thereafter form saidelectrical discharge directed between said electrodes.
 35. The methoddefined in claim 32 wherein said fusible conductor is fed toward saidfirst electrode along said path through a fixed distance and thereaftersaid other electrode is advanced transversely toward said conductor to apoint at which dielectric breakdowns occur in said fluid medium betweensaid conductor and said electrodes to impulsively destroying theconductor and thereafter form a direct discharge between saidelectrodes.
 36. The method defined in claim 32 wherein said otherelectrode is brought into contact with said fusible conductor and saidfusible conductor is then advanced along said path toward said firstelectrode until dielectric breakdown occurs in the gap between saidconductor and said first electrode to explosively destroying saidconductor and then form a direct discharge between said electrodes. 37.The method defined in claim 32 wherein said other electrode is fed to apredetermined point adjacent said path and defines a gap with saidfusible conductor, and said fusible conductor is then advanced alongsaid path to reduce the gap between itself and said first electrode to apoint at which dielectric breakdown occurs across both gaps toexplosively destroying said conductor and thereafter form a directelecTrical discharge between said electrodes.
 38. An apparatus forforming a workpiece by deformation thereof or kinetic deposition ofmaterial thereon with a shock wave generated by a discharge in a fluidmedium and transmitted by said medium to the workpiece, said apparatuscomprising: a first electrode; means for directing an electricallydestructible conductor in the region of said electrode along a feedpath; means for passing an electrical-current pulse through saidelectrically destructible conductor, thereby destroying said conductorexplosively and generating the discharge in said fluid medium; and afurther electrode disposed along said path adjacent said conductor andspaced from said means for directing said conductor along said path andsaid first electrode, said means for passing said electrical currentpulse through said conductor being connected across said electrodes todevelop a discharge therebetween upon explosive destruction of saidconductor.
 39. A method of deforming a workpiece or kineticallydepositing material thereon by applying to said workpiece a shock wavegenerated by electrical discharge between a pair of electrodes spacedapart in a dielectric medium, said method comprising the steps offeeding an electrically destructible conductor along a predeterminedpath toward one of said electrodes, the other of said electrodes beingdisplaceable toward and away from said path; connecting a source ofstored electrical energy across said electrodes; and relativelydisplacing said electrically destructible conductor and at least one ofthe electrodes to reduce the gap between them and effect a dielectricbreakdown in said fluid medium to generate a discharge and explosivedestruction of said conductor.
 40. In a method of hydroimpact forming aworkpiece by directing a power jet of a liquid in shock-transmittingrelationship therewith, the improvement which comprises controlling atleast one parameter of said power jet by directing generallytransversely thereto a control jet of a fluid at a pressure less thanthat of said power jet.
 41. The improvement defined in claim 40 whereinsaid power jet of liquid directed by generating an impulsive electricaldischarge in said liquid.
 42. In an apparatus for the hydroimpactforming of a workpiece by directing a power jet of a liquid inshock-transmitting relationship therewith through a barrel, theimprovement which comprises means along the path of said power jet forcontrolling at least one parameter of said power jet and including acontrol nozzle trained transversely to and against said power jet andmeans for supplying a control fluid to said nozzle.
 43. The improvementdefined in claim 42 wherein said power jet is directed by generating animpulsive electric discharge in said liquid within said barrel.
 44. In amethod of hydroimpact forming a workpiece into an intricate shape havinga plurality of recesses by sweeping masses of a high-velocity liquidpower jet in shock-transmitting relationship over said workpiece, theimprovement which comprises controlling a parameter of said masses inaccordance with the configurations of said recesses.
 45. The improvementdefined in claim 44 wherein said parameter is at least one of thevelocity and the configuration of said mass.
 46. An apparatus forhydroimpact forming of a workpiece into an intricate shape, comprising adie having a plurality of recesses; means for projecting a high-velocitypower jet in shock-transmitting relationship against a workpiecejuxtaposed with said die so that said jet sweeps across said recesses todeform said workpiece into same; and means for controlling a parameterof said power jet in accordance with the configurations of saidrecesses.
 47. The apparatus defined in claim 46 wherein thelast-mentioned means is so constructed and arranged as to control thevelocity of said power jet.
 48. The apparatus defined in claim 46wherein the last-mentioned means is so constructed and arranged as tOcontrol the configuration of said power jet.
 49. A method defined inclaim 31 wherein said discharge is generated by an electrical pulseincluding an initial high-voltage, low-current breakdown componentfollowed by a low-voltage, high-current component sustaining thedischarge.